What is agar?
Agar, also known as agar agar, is a gelatinous substance formed by polysaccharides from the cell wall of seaweed. It is considered one of the most necessary tools in the branch of biology.
Many centuries ago it was used in the cuisine of the far east, although it was not until the middle of the nineteenth century when its use spread throughout Europe. It´s uses included thickening and rinsing of foods as varied as ice cream and the beer, respectively.
However, what is not usually known is that it originated in the kitchen of a humble German marriage.
Since then, its use is more than widespread in laboratories; from those of microbiology, in which it is used as selective medium for the cultivation of certain types of microorganisms, until those of molecular biology, in which its porosity is used for the size separation of some particles.
How the agar passed from the kitchens to the laboratories
In 1881, a young doctor, named Walther Hesse, decided to take his work beyond the simple treatment of patients in a rural village in which he was destined, focusing also on bacteriology and how environmental pollution and poor hygiene could lead to the spread of diseases.
In order to do this, he collected several samples of air and water in order to cultivate the bacteria present in them, but he came across a big problem when he found that the gelatine he had used melted with the warm summer temperatures, becoming liquid and spoiling the whole experiment.
Sorry for the problem and not knowing how to solve it, one day he decided to share his regret with his wife, Angelina Fanny Eilshemius, who quickly extrapolated the situation to the desserts she made in her kitchen, since she could cook cakes and jellies without the problem of the melting gelatine.
The young woman used agar, an algae-based material that had been used by her family for many years. Using it did not seem far fetched, so Walther decided to take a sample of the precious ingredient, to try to sow on him the samples he had collected for his investigations.
To his surprise he saw that agar was indeed a magnificent planting medium, because it provided the necessary nutrients, while it remained stable, without deteriorating because of the high temperatures or enzymes secreted by the bacteria themselves . In addition, as a result, it could be sterilized without problems, while offering multiple possibilities for cultures of all types of bacteria, including slow-growing bacteria.
Nowadays there are endless options within the agar, as they are added to other resources, such as certain antibiotics or selective dyes, which make it possible to discern whether a particular type of bacteria is growing in the medium.